Insulation detection circuit and vehicle-mounted charger

Abstract

This application discloses an insulation detection circuit and an on-board charger, belonging to the field of new energy technology. The insulation detection circuit includes: a sampling module for sampling the output live wire and neutral wire voltage divider; a switching module connected between the sampling module and a bias node, configured to be turned on when the on-board charger is operating in inverter mode, so that the sampling module outputs a sampling voltage to the bias node; a bias module for applying a bias voltage to the sampling voltage; and an output module for adding the biased sampling voltage. By providing a switching module, this application realizes the on / off control between the insulation detection circuit and the output live wire and output neutral wire. The switching module is turned on when the on-board charger is operating in inverter mode, avoiding the influence of the sampling module on the insulation resistance of the neutral and live wires to ground under other operating conditions, thus ensuring the insulation performance of the on-board charger in non-inverter mode.

Description

Technical Field

[0001] This application relates to the field of new energy technology, specifically to an insulation detection circuit and an on-board charger. Background Technology

[0002] With the popularization of on-board charger (OBC) technology for electric vehicles, its inverter discharge function has been widely used. In inverter mode, the AC output terminals (live wire L, neutral wire N) of the on-board charger directly supply power to the outside. If the insulation resistance between the live wire or neutral wire and ground decreases or a short circuit occurs, it will directly lead to the risk of electric shock to personnel. Therefore, it is necessary to perform insulation testing on the insulation status under inverter conditions.

[0003] The relevant insulation detection circuit samples the circuit by connecting a voltage divider resistor between the neutral and live wires and ground. However, under other operating conditions, such as in forward charging mode, this voltage divider resistor will reduce the insulation resistance of the neutral and live wires to ground, posing a safety hazard of insulation failure. Therefore, it is difficult to meet the insulation performance requirements of the on-board charger in non-inverter mode. Summary of the Invention

[0004] An insulation detection circuit and an on-board charger are provided to solve the technical problem that the insulation detection circuit reduces the insulation resistance of the neutral and live wires to ground in non-inverter mode, making it difficult to meet the insulation performance requirements of the on-board charger.

[0005] In a first aspect, embodiments of this application provide an insulation detection circuit, comprising: The sampling module includes a first sampling unit for sampling the output live wire voltage divider and a second sampling unit for sampling the output neutral wire voltage divider. A switching module is connected between the sampling module and the bias node, the bias node including a first bias node and a second bias node; the switching module is configured to be turned on when the on-board charger is operating in inverter mode, so that the first sampling unit outputs a first sampling voltage to the first bias node, and the second sampling unit outputs a second sampling voltage to the second bias node; A bias module is used to apply a first bias voltage to the first sampling voltage and to apply a second bias voltage to the second sampling voltage; The output module is used to add the first sampled voltage and the second sampled voltage after applying the bias, and output the detection voltage. The controller is used to detect the detection voltage and obtain the insulation detection result.

[0006] In one embodiment of this application, the insulation detection circuit further includes a driving module connected to the switching module. The driving module is configured to drive the switching module to conduct when the on-board charger is operating in inverter mode; and to drive the switching module to turn off when the on-board charger is operating in forward mode, so as to isolate the sampling module from the bias node.

[0007] In one embodiment of this application, the biasing module includes: Bias power supply; A first voltage divider unit is connected between the bias power supply and the first bias node to divide the output voltage of the bias power supply so as to output the first bias voltage to the first bias node. The second voltage divider unit is connected between the bias power supply and the second bias node, and is used to divide the output voltage of the bias power supply to output the first bias voltage to the second bias node.

[0008] In one embodiment of this application, the output module includes an impedance matching unit and an adder unit; The input terminals of the impedance matching unit are connected to the first bias node and the second bias node respectively. The impedance matching unit is used to perform impedance matching on the first sampled voltage and the second sampled voltage after applying bias, and outputs the first sampled voltage and the second sampled voltage after impedance matching. The input terminal of the addition unit is connected to the output terminal of the impedance matching unit. The addition unit is used to add the first sampled voltage and the second sampled voltage after impedance matching and output the detection voltage.

[0009] In one embodiment of this application, the impedance matching unit includes: A first operational amplifier, wherein the first input terminal of the first operational amplifier is connected to the first bias node, and the output terminal of the first operational amplifier is connected to the second input terminal of the first operational amplifier and the first input terminal of the addition unit; The second operational amplifier has its first input terminal connected to the second bias node, and its output terminal connected to both its second input terminal and the second input terminal of the adder unit.

[0010] In one embodiment of this application, the impedance matching unit further includes: The third resistor has a first end connected to the output terminal of the first operational amplifier and a second end connected to reference ground. The third resistor is used to provide a DC feedback path to the first operational amplifier. The fourth resistor has its first end connected to the output terminal of the second operational amplifier and its second end connected to reference ground. The fourth resistor is used to provide a DC feedback path to the second operational amplifier.

[0011] In one embodiment of this application, the addition unit further includes a filtering section connected to the output terminal of the addition unit for filtering the detected voltage.

[0012] In one embodiment of this application, the switching module includes at least one of a relay, an insulated gate bipolar transistor, a metal-oxide-semiconductor field-effect transistor, and a thyristor.

[0013] In one embodiment of this application, the first sampling unit includes a plurality of first resistors connected in series between the output live wire and the reference ground; the second sampling unit includes a plurality of second resistors connected in series between the output neutral wire and the reference ground; the total resistance of the first sampling unit is equal to the total resistance of the second sampling unit and is greater than or equal to 20M ohms.

[0014] An on-board charger includes an inverter circuit and the aforementioned insulation detection circuit. The insulation detection circuit is connected to the output live wire and output neutral wire of the inverter circuit. The insulation detection circuit is configured to perform insulation detection on the inverter circuit when the on-board charger is operating in inverter mode.

[0015] The beneficial effects of this application are as follows: This application provides a switch module to realize the on / off control between the insulation detection circuit and the output neutral and live wires. The switch module is configured to be turned on when the on-board charger is operating in inverter mode. Therefore, the insulation detection circuit will only be connected to the inverter circuit in inverter mode, avoiding the influence of the sampling module on the insulation resistance of the neutral and live wires to ground under other operating conditions, and ensuring the insulation performance of the on-board charger in non-inverter mode. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is an architectural diagram of the insulation detection circuit provided in an embodiment of this application; Figure 2 This is a circuit diagram of the insulation detection circuit provided in the embodiments of this application; Figure 3 This is a schematic diagram showing the connection between the insulation detection circuit and the inverter circuit provided in the embodiments of this application; Figure 4 This is a waveform diagram of the sampled voltage under normal insulation conditions provided in the embodiments of this application; Figure 5 This is a sampled voltage waveform diagram under insulation abnormality conditions provided in the embodiments of this application.

[0018] Explanation of reference numerals in the attached figures: 1. Sampling module; 11. First sampling unit; 12. Second sampling unit; 2. Switching module; 3. Bias module; 31. First voltage divider unit; 32. Second voltage divider unit; 4. Output module; 41. Impedance matching unit; 42. Adder unit; 5. Controller; 6. Inverter circuit; 7. Insulation detection circuit; P1. First bias node; P2. Second bias node; V1. Bias power supply; V2. Drive power supply; K1. Relay; U1. First operational amplifier; U2. Second operational amplifier; L. Output live wire; N. Output neutral wire; R1. First resistor; R2. Second resistor; R3. Third resistor; R4. Fourth resistor; R5. Fifth resistor; R6. Sixth resistor; R7. Seventh resistor; R8. Eighth resistor; R9. Ninth resistor; R10. Tenth resistor; C1. First capacitor; C2. Second capacitor; Y1. First safety capacitor; Y2. Second safety capacitor. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] Embodiments of this application provide an insulation detection circuit, such as Figure 1 As shown, it includes: The sampling module 1 includes a first sampling unit 11 for sampling the output live wire L by voltage division, and a second sampling unit 12 for sampling the output neutral wire N by voltage division. Switching module 2 is connected between sampling module 1 and bias node, bias node including first bias node P1 and second bias node P2; switching module 2 is configured to be turned on when the on-board charger is operating in inverter mode, so that the first sampling unit 11 outputs a first sampling voltage to the first bias node P1 and the second sampling unit 12 outputs a second sampling voltage to the second bias node P2. The bias module 3 is used to apply a first bias voltage to the first sampling voltage and to apply a second bias voltage to the second sampling voltage; Output module 4 is used to add the first sampled voltage and the second sampled voltage after applying the bias, and output the detection voltage. Controller 5 is used to detect the detection voltage and obtain the insulation test results.

[0022] The insulation detection circuit of this application is applied in an on-board charger to perform insulation detection during the inverter operation of the on-board charger. The first sampling unit 11 performs voltage division sampling on the output live wire L to obtain a first sampling voltage; the second sampling unit 12 performs voltage division sampling on the output neutral wire N to obtain a second sampling voltage. The switching module 2 is only turned on when the on-board charger is operating in inverter discharge mode, allowing the first sampling voltage to flow to the first bias node P1 and the second sampling voltage to flow to the second bias node P2. When the on-board charger is operating under other conditions, the switching module 2 remains off, isolating the sampling module 1 from the bias node and preventing any impact on the insulation resistance of the neutral and live wires to ground.

[0023] Since the sampling module 1 outputs an AC signal, and the controller 5 interface cannot receive negative voltage, this application applies a DC bias to the first and second sampling voltages output by the sampling module 1 through the bias module 3, so that the voltage waveforms output by the sampling module 1 are all positive and can be received by the controller 5.

[0024] Output module 4 is used to add the first and second sampled voltages after applying bias, and output the detection voltage. Controller 5 is used to perform waveform detection on the detection voltage to obtain the insulation detection result. Under normal insulation conditions, the voltage amplitudes of the live wire and neutral wire to ground are equal but their phases are opposite, such as... Figure 4 As shown. Therefore, the detection voltage output by output module 4 is a constant value. However, in the event of an insulation abnormality, the detection voltage will fluctuate, such as... Figure 5 As shown, controller 5 performs waveform detection on the detected voltage as described above, thereby outputting an insulation detection result to determine whether the insulation is normal. This enables real-time monitoring of the insulation resistance between the output live wire L or neutral wire of inverter circuit 6 and the vehicle body during reverse inverter discharge of the on-board charger, preventing electric shock to personnel.

[0025] This application provides a switch module 2 to control the connection and disconnection between the insulation detection circuit and the output neutral line N and the output live line L. The switch module 2 is configured to be turned on when the on-board charger is operating in inverter mode. The insulation detection circuit will only be connected to the inverter circuit 6 in inverter mode, which avoids the influence of the sampling module 1 on the insulation resistance of the neutral line and the live line to ground under other operating conditions, and ensures the insulation performance of the on-board charger in non-inverter mode.

[0026] In some embodiments, the insulation detection circuit further includes a drive module connected to the switch module 2. The drive module is used to drive the switch module 2 to conduct when the on-board charger is operating in inverter mode; and to drive the switch module 2 to turn off when the on-board charger is operating in forward mode, so as to electrically isolate the sampling module 1 from the bias node, avoid the sampling module 1 from reducing the insulation performance of the whole vehicle, and ensure insulation safety under charging conditions.

[0027] In some embodiments, such as Figure 2 As shown, the first sampling unit 11 includes multiple first resistors R1, which are connected in series between the output live wire L and the reference ground; the second sampling unit 12 includes multiple second resistors R2, which are connected in series between the output neutral wire N and the reference ground; the total resistance of the first sampling unit 11 is equal to the total resistance of the second sampling unit 12, and is greater than or equal to 20M ohms.

[0028] In some embodiments, the first sampling unit 11 and the second sampling unit 12 form a voltage divider circuit by connecting resistors in series, which can reduce the high voltage AC voltage (such as 220V / 380V AC output from the inverter) of the output live wire L and neutral wire to a low voltage first sampling voltage and second sampling voltage according to the total resistance value of the series resistors, so that the subsequent output module 4 can process it safely.

[0029] The total resistance of the first sampling unit 11 is equal to the total resistance of the second sampling unit 12, ensuring that the voltage division ratio of the two sampling circuits is consistent. The resistance values ​​of each first resistor R1 can be the same or different, and similarly, the resistance values ​​of each second resistor R2 can be the same or different. In other embodiments of this application, the first sampling unit 11 or the second sampling unit 12 may only have one first resistor R1 or second resistor R2 with a resistance value of 20M ohms or higher. However, the DC voltage that this resistor can withstand must be greater than 2800V.

[0030] In some embodiments, the switching module 2 includes at least one of a relay K1, an insulated gate bipolar transistor, a metal-oxide-semiconductor field-effect transistor, and a thyristor.

[0031] In some embodiments, taking the switch module 2 using a relay K1 as an example, the relay K1 is a double-pole double-throw relay K1. The first end of the coil of the relay K1 is connected to the driving power supply V2, and the second end of the coil of the relay K1 is connected to the reference ground. The first moving contact of the relay K1 is connected to the output terminal of the first sampling unit 11; the first normally open contact of the relay K1 is connected to the first bias node P1. The second moving contact of the relay K1 is connected to the output terminal of the second sampling unit 12; the second normally open contact of the relay K1 is connected to the second bias node P2.

[0032] The operating state of relay K1 is determined by the operating state of the on-board charger. When the on-board charger is operating in inverter mode, the drive module outputs a drive signal, energizing the coil of relay K1 and causing it to close. This connects the first moving contact and the first normally open contact of relay K1, allowing the first sampling unit 11 to connect to the first bias node P1 and output a first sampling voltage to P1. Simultaneously, the second moving contact and the second normally open contact of relay K1 connect, allowing the second sampling unit 12 to connect to the second bias node P2 and output a second sampling voltage to P2.

[0033] When the on-board charger is operating in non-inverter mode, such as in forward charging mode, the drive module stops outputting drive signals, causing the relay K1 coil to de-energize, opening the first moving contact and the first normally open contact, as well as the second moving contact and the second normally open contact. This disconnects the connection between the first sampling unit 11 and the first bias node P1, and the connection between the second sampling unit 12 and the second bias node P2, electrically isolating the neutral and live wires from the insulation detection circuit 7 to avoid reducing the overall vehicle insulation performance.

[0034] In some embodiments, the bias module 3 includes: Bias power supply V1; The first voltage divider unit 31 is connected between the bias power supply V1 and the first bias node P1, and is used to divide the output voltage of the bias power supply V1 so as to output the first bias voltage to the first bias node P1. The second voltage divider unit 32 is connected between the bias power supply V1 and the second bias node P2. It is used to divide the output voltage of the bias power supply V1 to output the first bias voltage to the second bias node P2.

[0035] In some embodiments, the first voltage divider unit 31 includes a fifth resistor R5 and a sixth resistor R6. The first end of the fifth resistor R5 is connected to the bias power supply V1, and the second end of the fifth resistor R5 is connected to the first bias node P1. The first end of the sixth resistor R6 is connected to the first bias node P1, and the second end of the sixth resistor R6 is connected to the reference ground. Taking an output voltage of 3.3V from the bias power supply V1 as an example, when the resistance values ​​of the fifth resistor R5 and the sixth resistor R6 are the same, the fifth resistor R5 and the sixth resistor R6 form a voltage divider structure, and the first bias node P1 is the voltage divider node of the fifth resistor R5 and the sixth resistor R6, obtaining a first bias voltage of 1.65V.

[0036] In some embodiments, the second voltage divider unit 32 includes a seventh resistor R7 and an eighth resistor R8. The first end of the seventh resistor R7 is connected to the bias power supply V1, and the second end of the seventh resistor R7 is connected to the second bias node P2. The first end of the eighth resistor R8 is connected to the second bias node P2, and the second end of the eighth resistor R8 is connected to the reference ground. Taking a 3.3V output voltage from the bias power supply V1 as an example, with the same resistance values ​​for the seventh resistor R7 and the eighth resistor R8, the second bias node P2 is the voltage divider node for the seventh resistor R7 and the eighth resistor R8, resulting in a second bias voltage of 1.65V.

[0037] The first voltage divider unit 31 and the second voltage divider unit 32 are symmetrical and employ identical voltage divider structures, ensuring that the resulting first bias voltage and second bias voltage are consistent, thus guaranteeing the accurate operation of the subsequent output module 4. Through the aforementioned first bias voltage and second bias voltage, the AC sampling signal, which originally fluctuated around 0V, is converted into a fully positive signal fluctuating around the bias voltage, adapting to the input range of the controller 5.

[0038] In some embodiments, the output module 4 includes an impedance matching unit 41 and an adder unit 42; The input terminals of the impedance matching unit 41 are connected to the first bias node P1 and the second bias node P2 respectively. The impedance matching unit 41 is used to perform impedance matching on the first sample voltage and the second sample voltage after applying the bias, and outputs the first sample voltage and the second sample voltage after impedance matching.

[0039] The input terminals of the adder unit 42 are connected to the output terminals of the impedance matching unit 41. The adder unit 42 is used to add the first sampled voltage and the second sampled voltage after impedance matching and output the detection voltage.

[0040] Because the bias node connects to sampling module 1 and the bias resistor, it exhibits a high output impedance. The adder unit 42, comprising several adder resistors, exhibits a low input impedance. Therefore, the adder unit 42 experiences a large load effect when receiving signals. If directly connected to the high-output-impedance bias node of the preceding stage, it would absorb the current from the preceding bias node, disrupting the amplitude and phase of the original first and second sampling voltages. Therefore, this application achieves impedance matching by setting an impedance matching unit 41 to output a low-output-impedance sampling signal, thereby avoiding signal distortion in the adder unit 42 and ensuring that the first and second sampling voltages can be accurately restored to the adder unit 42, improving the accuracy of the insulation judgment result.

[0041] In some embodiments, the impedance matching unit 41 includes: The first operational amplifier U1 has its first input terminal connected to the first bias node P1, and its output terminal connected to its second input terminal and the first input terminal of the adder unit 42, so that the first operational amplifier U1 operates in voltage follower mode. The output voltage of the first operational amplifier U1 is strictly equal to the input voltage, that is, the first sampling voltage after applying bias.

[0042] The second operational amplifier U2 has its first input terminal connected to the second bias node P2, and its output terminal connected to both its second input terminal and the second input terminal of the adder unit 42. This allows the second operational amplifier U2 to operate in voltage follower mode, where its output voltage is strictly equal to its input voltage, i.e., the second sampled voltage after applying bias.

[0043] In some embodiments, the impedance matching unit 41 further includes: The third resistor R3 has its first end connected to the output of the first operational amplifier U1 and its second end connected to the reference ground. The third resistor R3 is used to provide a DC feedback path to the first operational amplifier U1.

[0044] The fourth resistor R4 has its first end connected to the output of the second operational amplifier U2 and its second end connected to the reference ground. The fourth resistor R4 is used to provide a DC feedback path to the second operational amplifier U2.

[0045] Based on the above-mentioned operational amplifier, this application further adds a third resistor R3 and a fourth resistor R4. The third resistor R3 and the fourth resistor R4 are DC feedback resistors. The third resistor R3 is used to provide a DC feedback path to the first operational amplifier U1, and the fourth resistor R4 provides a DC feedback path to the second operational amplifier U2, so that the input bias current of the operational amplifier can be discharged to maintain a stable static operating point.

[0046] In some embodiments, the addition unit 42 further includes a filtering unit connected to the output terminal of the addition unit 42, which is used to filter the detected voltage.

[0047] In some embodiments, the filtering section includes a ninth resistor R9, a tenth resistor R10, a first capacitor C1, and a second capacitor C2. The first terminal of the ninth resistor R9 is connected to the output terminal of the first operational amplifier U1, the first terminal of the first capacitor C1 is connected to the second terminal of the ninth resistor R9, and the second terminal of the first capacitor C1 is connected to reference ground. The first terminal of the tenth resistor R10 is connected to the output terminal of the second operational amplifier U2, the first terminal of the second capacitor C2 is connected to the second terminal of the tenth resistor R10, and the second terminal of the second capacitor C2 is connected to the second terminal of the first capacitor C1. The output terminal of the adder unit 42 can be any one of the following: the connection node between the ninth resistor R9 and the first capacitor C1, the connection node between the first capacitor C1 and the second capacitor C2, or the connection node between the second capacitor C2 and the tenth resistor R10.

[0048] The embodiments of this application also provide an on-board charger, which includes an inverter circuit 6 and an insulation detection circuit 7 as described in the above embodiments. The insulation detection circuit 7 is connected to the output live wire L and the output neutral wire N of the inverter circuit 6. The insulation detection circuit 7 is configured to perform insulation detection on the inverter circuit 6 when the on-board charger is operating in inverter mode.

[0049] In some embodiments, the connection between the inverter circuit 6 and the insulation detection circuit 7 is as follows: Figure 3 As shown, the inverter circuit 6 includes a first safety capacitor Y1 connected between the output live wire L and the ground wire, and a second safety capacitor Y2 connected between the output neutral wire N and the ground wire. Taking the first safety capacitor Y1 and the second safety capacitor Y2 having the same capacitance value as an example, the expression for the voltage of the output live wire L to ground is:

[0050] Where UL represents the voltage of the output live wire L to ground (dimension: volts V); UAC represents the effective value of the AC voltage output by the on-board charger inverter (dimension: volts V); f represents the frequency of the inverter output AC power (dimension: hertz Hz); t represents the time (dimension: seconds s); CY1 represents the capacitance value of the first safety capacitor Y1 (dimension: farads F); CY2 represents the capacitance value of the second safety capacitor Y2 (dimension: farads F).

[0051] The expression for the voltage of the output neutral line N to ground is:

[0052] UN represents the voltage of the output neutral line N to ground (dimension: volts V).

[0053] The first sampling unit 11 of the insulation detection circuit 7 is connected between the output live wire L and the switch module 2, and the second sampling unit 12 is connected between the output neutral wire N and the switch module 2. Taking the switch module 2 as an example, the contacts of the relay K1 only engage when the on-board charger is operating in inverter mode. This prevents abnormal reduction in insulation resistance due to short circuit failure of the first sampling unit 11 or the second sampling unit 12, which could endanger personal safety from electric shock. The bias module 3 provides a first bias voltage and a second bias voltage, respectively, for the first sampling voltage output by the first sampling unit 11 and the second sampling voltage output by the second sampling unit 12, to prevent the controller 5 from receiving a negative voltage. The typical value of the bias voltage in this embodiment is 1.65V. The output module 4 adds the first and second sampling voltages after applying the bias and outputs the detection voltage; the controller 5 performs waveform detection on the detection voltage to obtain the insulation detection result.

[0054] When the on-board charger operates in inverter mode, the capacitance values ​​of the safety capacitors connected to ground for the output live wire (L) and the output neutral wire (N) are equal. The presence of these safety capacitors ensures that both the output live wire (L) and the output neutral wire (N) have voltages connected to ground, with a 180° phase difference. The magnitude of these voltages is proportional to the capacitance values ​​of the output live wire (L) and the output neutral wire (N). Under normal insulation resistance conditions, such as… Figure 4 As shown, the voltage between the live wire and ground and the voltage between the neutral wire and ground have the same amplitude but opposite phase, so the sum of the two voltages is a constant value. After passing through sampling module 1 and bias module 3, the amplitude decreases proportionally, and the controller 5 detects a constant value, indicating that the insulation is normal. When the insulation resistance fails, such as Figure 5 As shown, if the voltage of the output live wire L or the output neutral wire N to ground becomes unbalanced, the sum of the voltages of the output live wire L and the output neutral wire N to ground will no longer be a constant value. The controller 5 will detect a voltage that is no longer constant, but rather an AC signal. At this point, it determines that the insulation has failed and commands the inverter circuit 6 to stop working to prevent electric shock.

[0055] The above provides a detailed description of an insulation detection circuit and an on-board charger provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An insulation detection circuit, characterized by comprising: include: The sampling module includes a first sampling unit for sampling the output live wire voltage divider and a second sampling unit for sampling the output neutral wire voltage divider. A switching module is connected between the sampling module and the bias node, the bias node including a first bias node and a second bias node; the switching module is configured to be turned on when the on-board charger is operating in inverter mode, so that the first sampling unit outputs a first sampling voltage to the first bias node, and the second sampling unit outputs a second sampling voltage to the second bias node; A bias module is used to apply a first bias voltage to the first sampling voltage and to apply a second bias voltage to the second sampling voltage; The output module is used to add the first sampled voltage and the second sampled voltage after applying the bias, and output the detection voltage. The controller is used to detect the detection voltage and obtain the insulation detection result.

2. The insulation detection circuit according to claim 1, characterized by The insulation detection circuit further includes a drive module connected to the switch module. The drive module is used to drive the switch module to conduct when the on-board charger is operating in inverter mode; and to drive the switch module to turn off when the on-board charger is operating in forward mode, so as to isolate the sampling module from the bias node.

3. The insulation detection circuit according to claim 1, characterized by The bias module includes: Bias power supply; A first voltage divider unit is connected between the bias power supply and the first bias node to divide the output voltage of the bias power supply so as to output the first bias voltage to the first bias node. The second voltage divider unit is connected between the bias power supply and the second bias node, and is used to divide the output voltage of the bias power supply to output the first bias voltage to the second bias node.

4. The insulation detection circuit according to claim 1, characterized by The output module includes an impedance matching unit and an adder unit; The input terminals of the impedance matching unit are connected to the first bias node and the second bias node respectively. The impedance matching unit is used to perform impedance matching on the first sampled voltage and the second sampled voltage after applying bias, and outputs the first sampled voltage and the second sampled voltage after impedance matching. The input terminal of the addition unit is connected to the output terminal of the impedance matching unit. The addition unit is used to add the first sampled voltage and the second sampled voltage after impedance matching and output the detection voltage.

5. The insulation detection circuit according to claim 4, characterized in that, The impedance matching unit includes: A first operational amplifier, wherein the first input terminal of the first operational amplifier is connected to the first bias node, and the output terminal of the first operational amplifier is connected to the second input terminal of the first operational amplifier and the first input terminal of the addition unit; The second operational amplifier has its first input terminal connected to the second bias node, and its output terminal connected to both its second input terminal and the second input terminal of the adder unit.

6. The insulation detection circuit according to claim 5, characterized in that, The impedance matching unit further includes: The third resistor has a first end connected to the output terminal of the first operational amplifier and a second end connected to reference ground. The third resistor is used to provide a DC feedback path to the first operational amplifier. The fourth resistor has its first end connected to the output of the second operational amplifier and its second end connected to reference ground. The fourth resistor is used to provide a DC feedback path to the second operational amplifier.

7. The insulation detection circuit according to claim 4, characterized by The addition unit further includes a filtering section, which is connected to the output terminal of the addition unit and is used to filter the detected voltage.

8. The insulation detection circuit of claim 1, wherein The switching module includes at least one of a relay, an insulated gate bipolar transistor, a metal-oxide-semiconductor field-effect transistor, and a thyristor.

9. The insulation detection circuit of claim 1, wherein The first sampling unit includes multiple first resistors connected in series between the output live wire and the reference ground; the second sampling unit includes multiple second resistors connected in series between the output neutral wire and the reference ground; the total resistance of the first sampling unit is equal to the total resistance of the second sampling unit and is greater than or equal to 20M ohms.

10. An on-board charger, characterized by, The on-board charger includes an inverter circuit and an insulation detection circuit as described in any one of claims 1 to 9, the insulation detection circuit being connected to the output live wire and output neutral wire of the inverter circuit, and the insulation detection circuit being configured to perform insulation detection on the inverter circuit when the on-board charger is operating in inverter mode.

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